The present disclosure relates to an image forming apparatus including a paper feed device and a method of controlling such an image forming apparatus.
An image forming apparatus that prints an image on a sheet to output it incorporates a print portion including: an image forming portion which forms a toner image to transfer it to the sheet; a body paper feed portion that feeds the sheet to the image forming portion; and a fixing portion that fixes the toner image transferred to the sheet. A paper feed device (option device) that feeds the sheet to the print portion may be fitted to the image forming apparatus separately from the body paper feed portion.
The paper feed device takes out a sheet held in a cassette or the like, and transports the sheet to a sheet transport path connected to the print portion. Hence, in the paper feed device, a paper feed transport portion for feeding and transporting the sheet to the sheet transport path connected to the print portion is provided. The paper feed transport portion includes a roller and a motor, rotates the roller by the drive force of the motor and thereby feeds and transports the sheet. In other words, the paper feed device receives power supplied from a power supply portion to perform a paper feed transport operation.
Multi-stage paper feed devices may be fitted to the image forming apparatus. For example, multi-stage paper feed devices are stacked in an up/down direction, and the paper feed transport portions (paper feed transport paths) of the multi-stage paper feed devices are coupled to each other.
In this configuration, when a sheet held in a lower stage paper feed device than a predetermined stage is fed to the print portion, the predetermined stage paper feed device (paper feed transport portion) together with the lower stage paper feed device (paper feed transport portion) performs the paper feed transport operation of the sheet. On the other hand, when a sheet held in the predetermined stage paper feed device is fed to the print portion, it is not necessary to make the lower stage paper feed device (paper feed transport portion) than the predetermined stage perform the paper feed transport operation of the sheet. Hence, when the sheet held in the predetermined stage paper feed device is fed to the print portion, in order to reduce power consumption, it is possible to stop power supply to the lower stage paper feed device (paper feed transport portion) than the predetermined stage.
For example, it is assumed that a paper feed device which holds the sheet of a frequently used sheet size is the uppermost stage paper feed device (the paper feed device close to the print portion). In this case, the uppermost stage paper feed device feeds the sheet more frequently (only the uppermost stage paper feed device is made to perform the paper feed transport operation for a longer period of time). Hence, it is possible to stop the power supply to the second and subsequent paper feed devices (paper feed transport portions) for a longer period of time. Consequently, the effect of power saving is enhanced.
However, in general, the sheet size of sheet that can be held in each of the multi-stage paper feed devices can be changed. Hence, the paper feed device that holds the sheet of the frequently used sheet size is not always the uppermost stage paper feed device. For example, the paper feed device that holds the sheet of the frequently used sheet size may be the lowermost stage paper feed device. In this case, the lowermost stage paper feed device feeds the sheet more frequently. When the lowermost stage paper feed device feeds the sheet, since it is necessary to make the other paper feed devices (paper feed transport portions) perform the paper feed transport operation of the sheet, it is impossible to stop the power supply to the other paper feed devices (paper feed transport portions). Consequently, it is impossible to obtain the effect of power saving.